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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

344

LIGHTING OILS

one form of apparatus to another, so that comparable data are obtainable
only with one and the same instrument under identical conditions.

The apparatus used officially in Italy and also in Great Britain, Germany
and Austria is that of Abel, improved by Pensky (Fig. 44). The oil is
placed in a brass cylinder A, tinned inside and furnished with a gauge index
I. Its cover carries a thermometer t with a scale extending from 10° to
50° and divided into half-degrees, and a clockwork mechanism m set in
motion by a lever a. Pressure of the latter opens automatically a small
window in the cover and at the same time lowers a small flame in b to the

aperture and then raises it again,
the window immediately closing.
The entire movement should occupy
two seconds.

The vessel A is heated by a water
bath B, the intermediate space C
being left empty, and is supported
on an ebonite ring fixed to the bath
B. The latter contains a thermo-
meter T with a red mark at 55°.
The bath is first heated to this
temperature, the covered vessel con-
taining the oil up to the prescribed
level being fitted and the ther-
mometer t in the oil read. For each
rise of temperature of 0-5° the clock-
work mechanism is operated, the
test being repeated until the flame
causes a small explosion : the tem-
perature then shown is the flash
point and should be corrected for
the pressure (+ 0-035° Per * ft1111-
below or above 760 mm.), the result
FlG_ 44                            being returned to the nearest half-

degree.

The dimensions of all parts of the apparatus are exactly controlled
and with careful working the results should not vary by more than 0-5-1°
at the most.

5.  Temperature   of   Ignition.—When  the   flash   point   has  been
measured, the cover of the vessel A is removed and a thermometer sup-
ported in the oil, the heating being continued and, after each i° rise, a
flame brought near the surface of the liquid without touching it.    When
the oil fires, the temperature is observed, the thermometer immediately
withdrawn and the oil extinguished with an asbestos card.

6.  Determination of the Viscosity.—This is not usually carried out
with illuminating oil, but it may, if required, be effected as in heavy oils
(q.v., Physical Tests, 7)  or, more exactly, by means of the Ubbelohde
viscorneter.1

1 Petroleum, 1909, IV, p. 861,

-called (Naphtha C)